The present invention relates to an improvement in the foundation system used on prefabricated structures, such as mobile homes or factory manufactured buildings. More specifically, a foundation system made of a plurality of precast panels that rest on precast posts and not only support the panels but also close in the space between the lower surface of the structure in a manner that is both weather tight and aesthetically pleasing.
In the past, prefabricated structures were positioned at their building sites by the use of a poured concrete slab or conventional concrete footings. The use of these foundation systems created two separate problems. The first of these is that they are relatively labor and material intensive resulting in higher costs that to some degree offset the cost saving advantages that are inherent in the factory built methods of constructing housing or other buildings.
Secondly, these types of foundation systems require an additional mechanism to close off the open space between the bottom surface of the structure's rim joist and the surface of the ground. Typically, this space is closed off by the use of wood, vinyl or sheet metal skirting material. The use of these materials is undesirable because they form a barrier that is insecure and that requires a great deal of maintenance to keep it in a good state of repair. Additionally, the use of such construction materials does not provide a weather tight structure that is often necessary in such structures, especially when they are placed in northern areas where there is a need to provide an insulated space between the structure and the surface of the ground. Finally, the use of these materials results in a finished appearance that clearly indicates that it is a prefabricated structure instead of site-built which is an undesirable result to the eventual owner.
The prior art has examples of attempts to resolve these problems. The first of these is illustrated in U.S. Pat. No. 5,067,289 issued to Ouderkirk which provides a unified wooden foundation and skirting system for these types of structures. The most obvious problems with this solution is that the use of wood for this purpose is that it results in a foundation system that lacks in structural integrity and which is susceptible to durability problems associated with weathering and material rot. Additionally, this foundation system requires the use of a plurality of foundation units being placed in the center area of the structure for further support. This adds a degree of difficulty to the operation as it requires that all of these additional structural components be placed in a manner so that they are all exactly level in relation to themselves and the remaining components of the foundation.
A further solution to this problem is offered in U.S. Pat. No. 6,125,597 issued to Hoffman which provides a foundation and skirting system that employs a plurality of precast concrete panels resting on footing blocks positioned in the ground. The precast panels provide both the foundation and skirting for the prefabricated structure and the blocks are secured in position by the use of anchor rods that extend through them and down into the ground. The problem with this solution is that the placement of the blocks requires the builder dig a trench and prepare that exposed surface in a manner that will adequately support the blocks and the weight of the structure that they carry. This method of construction can result is a susceptibility to settling due to inconsistent ground conditions and types. Additionally, it does not provide a mechanism by which the foundation can compensate for frost heaving conditions that are common in colder climates. Finally, the provided anchoring system for the footing blocks is not secure enough when considering the loads that they must carry during the course of the structure's life.
Therefore, it can be seen that it would be desirable to provide a method of securing a prefabricated structure to a building site that takes advantage of the cost effective nature of such buildings in a manner that not only effectively secures the structure in place but also closes off the area between the bottom of the structure on the surface of the earth. Additionally, it would be desirable to provide a means of closing off this area in a manner that results in an insulated interior space and which results in a finished structure that adds to the aesthetic value of the structure by providing an end product that closely mimics the look of a site built unit.